ML18038B792

LER 96-008-00:on 961101,MS SR Valves Exceeded TS Required Setpoint Limit as Result of Disc/Seat Bonding.Caused by Corrosion Bonding of SRV Pilot Interface.Replaced All Thirteen Ms SR Valve Pilot cartridges.W/961127 Ltr

ML18038B792
Person / Time
Site:	Browns Ferry
Issue date:	11/27/1996
From:	Machon R, Matherly D TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-96-008-02, LER-96-8-2, NUDOCS 9612030304
Download: ML18038B792 (18)

Text

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1) REGULATC TNEORMATION DZSTRTBUTTON STEM (RTDS)

ACCESSION NBR:9612030304 DOC.DATE: 96/11/27 NOTARIZED: NO DOCKET FACIL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 AUTH..NAME AUTHOR AFFILIATION MATHERLY,D.C. Tennessee Valley Authority MACHON,R.D. Tennessee Valley Authority REC I P . NAME RECIPIENT AFFILIATION

SUBJECT:

LER 96-008-00:on 961101,MS SR valves exceeded TS required setpoint limit as result of disc/seat bonding. Caused by corrosion bonding of SRV pilot interface. Replaced all thirteen MS SR valve pilot cartridges.W/961127 ltr.

DISTRIBUTION.CODE: IE22T COPIES RECEIVED:LTR ) ENCL ( SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rp , etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES 1D CODE/NAME LTTR ENCL ZD.CODE/NAME LTTR ENCL PD2-3-PD 1 1 WILLIAMS,J. 1 1 INTERNAL: ACRS 1 1 AEOD/SPD RAB 2 2 AEOD/SPD/RRAB 2 2 NTER 1 1 NRR/DE/ECGB 1 1 1 1 NRR/DE/EMEB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HI CB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRCH/HQMB 1 1 NRR/DRPM/PECB 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 RES/DET/EIB 1 1 RGN2 FILE 01 1 1 D EXTERNAL: L ST LOBBY WARD 1 1 LITCO BRYCEI J H 1 1 NOAC MURPHY,G.A 1 1 NOAC POORE,W. 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM OWFN SD-5(EXT. 415-2083) TO ELIMINATE YOUR NAME FROM DISTRiBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 26 ENCL 26

Jg Tennessee Vasey Authonty. pos; Oltce Box 2000. Decat t . pJaoa~ ao609.2000 R. D. (Rick) Machon Vce president, 8rowns Ferry Nvctear ptanl November .27, 1996 10 CFR 50.73 U'.S. Nuclear Regulatory Commission ATTN.: Document Control Desk Washington, D.C. 20555

Dear Sir:

BROGANS FERRY 'NUCLEAR PLANT tBFN) UNIT 2 - DOCKET NO 50-260 FACILITY OPERATING LICENSE DPR-52 - LICENSEE EVENT REPORT 50-260/96008 The enclosed report provides details concerning the Unit 2 main steam safety/relief valves exceeding the technical specifications setpoint limit during tests. This report is

.submitted in accordance with 10 CFR 50.73(a)(2) (i) (B) as a condition prohibited by the plant s technical specifications.

Sincerely, Enclosure cc: See page 2 96i20303 0 PDR ADQCK 5

U.S..Nuclear Regulatory Commission Page 2 Ndvember 27, 1996 Enclosure cc (Enclosure):

Mr. Mark S. Lesser, Branch Chief U.S. Nuclear Regulatory Commission Region II 101,Marietta Street, NW, Suite 2900

.Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611 Mr. J. F. Williams, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North

.11555 Rockville Pike Rockville, Maryland 20852

41 NRC FORM 366 NUCLEAR REGULATORY COMMISSION PROVED BY OMB No. 3150-0104 (4.96) EXPIRES 04/30/96 ESTIMATED BURDEN PER RESPONSE To COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST:

50.0 HRS. REPORTED LESSONS LEARNED ARE LICENSEE EVENT REPORT (LER) INCORPORATED INTO THE LICENSING PROCESS AND FED BACK To INDUSTRY. FORWARD COMMENTS REGARDING (See reverse for required number of BURDEN ESTIMATE To THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T-6 F33). U.S. NUCLEAR digits/characters for each block) REGULATORY COMMISSION, WASHINGTON. DC 20665 DOCKET NtiyIBER f11 PACE f3 I FACIUTY NAME (11 Browns Ferry Nuclear (BFN) Plant Unit 2 05000260 1OF6 TITLE fel Main Steam Safety/Relief Valves Exceeded the Technical Specifications Required Setpoint Limit as a Result of Disc/Seat Bonding EVENT DATE IS) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (6)

FACILITYNAME OOCKETNUMBER SEQUENTIAL REVISION MONTH DAY YEAR MONTH DAY YEAR NUMBER NUMBER NA 05000 FACIUTY NAME OOCKETNUMBER 01 96 96 008 00 11 27 96 NA 05000 OPERATING THIS REPORT IS SUBMITTED PURS UANT To THE REQUIREMENTS OF 10 CFR %: (Check one or more) (11)

MODE (9) N 20. 2201 (b) 20.2203 (a) (2) (v) X 50.73(a)(2)(i)(B) 50.73(a)(2)(viii) 20.2203(a)(l) 20.2203 (a) (3) (I) 50.73(a) (2)(ii) 50.73 (a) (2) (x)

POWER LEVEL (10) 0 20.2203(a) (2) (I) 20. 2203 (a) (3) (ii) 50.73(a)(2)(iii) 73.71 20.2203(a) (2) (ii) 20.2203 (a) (4) 50.73(a)(2)(iv) OTHER

20. 2203(a) (2) (iii) 50.36(c) (1) 50.73(a)(2)(v) Specify In Abetrect below or in NRC Form 366A 20.2203(a) (2) (iv) 50.36(c) (2) 50 73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER Bnorude Atee Code)

David C. Matherly, Operations Specialist (205) 729-2048 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13I REPORTABLE REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER To NPRDS To NPRDS X SB RV T020 SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED YES SUBMISSION (If yes, complete EXPECTED SUBMISSION DATE).

X No DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single. spaced typewritten lines) (16)

On November 1, 1996, Wyle Laboratories notified TVA that 10 of the 13 Unit 2 main steam safety/relief valves (SRV) pilot cartridges failed setpoint tolerance bench tests. This condition is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's technical specifications (TS). The pilot cartridges had been removed from the Unit 2 main steam SRVs following a failure to lift when reactor pressure exceeded the setpoint tolerance of the two lowest set groups of SRVs during a Unit 2 scram on October 29, 1996 (reported in LER 260/96007).

Testing by Wyle Laboratories discovered that the SRVs'as found" setpoints were outside the TS setpoint tolerance of +/- 11 psi. The cause was attributed to corrosion bonding of the SRV'pilot disc/seat interface re'suiting in drifting of the SRV setpoints. The Unit 2 main steam SRVs were installed during the Unit 2 Cycle 8 refueling outage. Three of the SRVs had pilot cartridges with platinum (pt) alloyed stellite pilot discs and ten of the SRVs had pilot cartridges with stellite discs. Setpoint drift is a generic concern experienced by utilities using Target Rock Two-Stage SRVs (Model No. 7567F) in boiling water reactors and is being investigated by the Boiling Water Reactors Owners Group (BWROG) SRV Drift Fix Development Committee and the manufacturer. TVA will continue to participate in the BWROG's evaluation of the long-term solution for the SRV setpoint drift problem. In addition, TVA will evaluate other possible solutions including use of pressure switch actuated SRVs and different applications of pt-stellite discs.

NRC FORM 366 I4.96)

!I NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTZNUATZON FACILITY NAME 1 LER NUMBER 6 PAGE 3 YEAR SEQU N IA REVISION NUMBER NUMBER Browns Ferry Unit 05000260 2 of 6 2

96 008 00 more epece e require, use e rrrone copiee o PLANT CONDITIONS At the time of the discovery of this conditi.on, Unit 2 was in a cold shutdown condition. Unit 3 was operating at 100 percent power. Unit 1 was shutdown and defueled.

DESCRIPTION OF EVENT A. Event, On November 1, 1996, TVA was notified that of the three main steam [SB) safety/relief valves (SRV) [RV) pilot platinum (pt) stellite disc cartridges and ten stellite cartridges testedr 's three pt-stellite and seven stellite cartri.dges failed t'e found'etpoint tolerance bench tests. The setpoints were found outside the TS tolerance of +/- 11 pounds per scpxare inch (psi)

(approximately 1 percent). See the attachment to this LER for speci.fic SRV test results.

The SRV pilot cartridges were removed from the unit 2 main steam SRVs (Target Rock Two-Stage SRV Model No. 7567F) and shipped to Wyle Laboratories for testing following a failure to lift when reactor pressure exceeded the setpoint tolerance of the two lowest set groups of SRVs during a scram occurring on October 29, 1996. This event was reported in LER 260/96007.

The above condition is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant' TS.

B~ Ino erable Structures Com onents or S stems that Contributed to the Event:

None.

C. Dates and A roximate Times of Ma'or Occurrences:

March 22-April 23, 1996 During the Unit 2 Cycle 8 refueling outage, the Unit 2 main steam SRV pilot cartridges were replaced.

October 29, 1996 Unit 2 scrammed. Measured reactor pressure reached approximately 1130 psig. No SRVs lifted.

October 30-November 1, 1996 Unit 2 main steam SRV pilot cartridges were removed and shipped to Wyle Laboratories for testing.

NRC FORM 366A (4-95)

II I i'

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4.95I LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 LER NUMBER 6 PAGE 3 AR UN IAL R ISION r NUMBER NUMBER Browns Ferry Unit 05000260 3 of 6 2

96 -- 008 00 mOf4 SPSC4 IS fOIIUlf4 ~ USO 4 IIIOhS COPIOS 0 0 fill, Laboratories notified TVA of November 1, 1996 Wyle the results of the bench tests.

's found'RV D. Other S stems or Seconda Functions Affected!

None.

E. Method of Discove c This condition was identified during valve bench testing at Wyle Laboratories in Huntsville, Alabama.

F. 0 erator Actions; None.

G. Safet S stem Res nses:

None.

III'AUSE OF THE EVENT A. Immediate Cause:

The immediate cause was SRV pilot disc/seat bonding resulting in

. the SRV setpoints deviating outside the TS setpoint tolerance of

+/- 11 psi.

B. Root Cause:

The cause of this bonding was attributed to corrosion at the two-stage SRV pilot disc/seat interface. This bonding caused the SRV setpoints to drift.

Corrosion bonding caused an increase in the valve opening pressure due to the need for additional opening force above the setpoint value.

IV. ANALYSIS OF'HE EVENT There are thirteen SRVS on the main steam piping. The valves are

. designed to perform the safety/relief function for the primary reactor system boundary by opening at a sensed pressure of 1105, 1115 or 1125 psig. ,The safety/relief function of the main steam SRVs is to limit primary reactor system pressure to less than 1375 psig in the event of a pressurization transient resulting from a turbine trip or a main steam isolation valve closure.

NRC FORM 366A (4.95)

0 0 ll

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION I4-95I LZCENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 AR S QUEN IAL ISION NUMBER NUMBER Browne Ferry Unit 05000260 4 of 6 2

96 -- 008 -- 00 more space rs require, use rtrons copies o orm TVA performed a limiting pressurization transient analysis for unit 2 cycle 6 assuming a spectrum of main steam SRV failures and setpoint drifts. The analysis concluded that even if four main steam SRVs completely fail to open and the remainder operate at ten percent above setpoint, the primary reactor system pressure would not exceed the TS safety limit of 1375 psig. Reload analyses performed by the fuel vendor and by TVA indicate that; the Main Steam Isolation Valve closure transient is not very sensitive to the changes in core loading.

Considering the conservative inputs to this analysis and the low sensitivity of the pressurization transient to cycle-by-cycle loading differences, the failures observed in this event would not have resulted in exceeding the TS safety limit during any abnormal operational transient. Thus, the plant and public safety would not have been adversely affected and safety of plant personnel was not compromised.

V. CORRECTIVE ACTIONS Immediate Corrective Actions:

All thirteen main steam safety/relief valve pilotrecertified cartridges were replaced with certified cartridges or tested and with their setpoint within TS requirements.

Bo Corrective Actions to Prevent Recurrence:

SRV setpoint drift is a generic concern experienced by utilities using this brand'f SRVs in boiling water reactors. and is being investigated by the BWROG' SRV Drift Fix Development Committee and the manufacturer.

TVA previously had implemented the BWROG recommendation of replacing SRV pilot cartridges with cartridges that have a 0.3 percent platinum (pt) alloyed stellite pilot disc. During the unit 2 cycle 8 refueling outage, three of the SRVs were replaced with the pt-stellite pilot disc cartridges and ten were replaced with stellite pilot disc cartridges.

The Wyle Laborat'ories'etpoint acceptance test results show that the,SRVs with the pt-stellite discs experienced setpoint drift comparable to the SRVs with stellite discs.

TVA will continue to participate in the BWROG' evaluation of the long-term solution for the SRV setpoint drift problem. In addition, because .the current application of pt-stellite discs has not solved the drift problem at Browne Ferry; TVA will evaluate other potential solutions including use of pressure switch actuated SRVs and different applications of pt-stellite discs. Long-term corrective actions associated with this problem will be tracked by the TVA corrective action program.

NRC FORM 366A I4 95I

I NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 UNIAL VI ION NUMBER NUMBER Browns Ferry Unit. 2 05000260 5 of 6 96 -- 008 -- 00 more spsce is require, use rtions copies o VI ~ ADDITIONAL INFORMATION A. Failed Com nents:

Target Rock,, Two-Stage SRVs Model No. 7567F.

B. Previous LERs on Similar Eventsc There have 'been several previous LERs'written concerning main steam SRV setpoint drift due to disc/seat corrosion bonding (LERs 260/87005,, 259/88053, 260/93003, 260/95003 and 260/96004).

VII ~ COMMITMENTS

'None.

Energy Industry Identification System (EIIS) system and component codes are identified in the text with brackets (e.g., [XX]).

NRC FOAM 366A I4.95)

~I

~t

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION I4-95)

LICENSEE EVENT REPORT (LER)

~

TEXT CONTINUATION FACILITY NAME 1 LER NUMBER 6 PAGE 3 YEAR S QU N IAL 'SION NUMBER NUMBER Browns Ferry Unit 05000260 6 of 6 2

96 -- 008 00 I more. epece re require, use nrone coppice o ATTACHMENT TO LER 260/96008 Ten of the following thirteen Unit 2 main steam SRVs failed to meet the required TS tolerance. Six served as Automatic Depressurization System (ADS) valves.-

Valve Pilot Disc Nameplate As-Found Percent Cartridge Composition Setpoint Actuation Difference Serial Number Pressure Pressure (>)

(S/N) (psi) (psi) 1078 stellite 1125 1135 + 0.89 1017 ADS stellite 1115 1240 +11.21 1079 pt-stellite 1115 1147 +2.87 1072 ADS stellite 1105 1183 +7.06 1232 ADS stellite 1115 1129 +1.26 1084 stellite 1105 1169 +5.79 1061 ADS stellite ~ 1115 1131 +1.43 1031 ADS stellite 1105 1141 +3.26 1060 ADS stellite 1105 1163 +5.25 1015 pt-stellite 1125 1183 +5.16 1032 pt-stellite 1125 1160 +3.11 1064 stellite 1125 1136 +0.98 1071 stellite 1125 1136 +0.98 NRC FOAM 366A I4.95)

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